In medium-low heat, toast whole coriander seeds on a dry frying pan. Remove from heat after the seeds turn brown. Using a mortar & pestle or a spice grinder, finely grind the Rumi Spice Coriander. Repeat steps with Rumi Spice Fennel and Rumi Spice Cumin (¾ tsp of whole coriander or cumin will yield around 1 tsp of ground coriander or cumin)
Mix ground cumin and remaining marinade ingredients together in a large bowl.
Add the chicken breasts to the bowl with the marinade, making sure they are covered in the mixture. Cover and refrigerate for one hour.
Heat oil in a large skillet or pan over medium heat.
Add chicken and brown for about 1 minute on both sides (it’s ok if it doesn’t cook through at this stage). Remove chicken and set aside.
Melt butter in the same pan and add onions. Sauté onions until soft then add garlic and ginger and cook for one more minute. Stir in tomatoes, ground coriander, garam masala, ground black cumin, red chili powder, and salt and continue to simmer on low until it becomes a thick, darker sauce - about 10 minutes.
Transfer the sauce to a bowl and use a hand mixer to puree the sauce or transfer to a blender and work in small batches. (Do not put all the sauce into the blender at once as the steam will cause the sauce to overflow when turned on.)
Pour the pureed sauce back in the pan. Stir in the heavy cream and sugar. Add in the chicken and continue to cook until chicken is cooked through - about 15 minutes
Garnish with chopped cilantro and serve with rice or naan bread.
